Rotor blades are used in conventional turbines to transfer kinetic energy, in the form of a medium such as gas under pressure, into rotary mechanical motion or, conversely, to transfer the mechanical energy of rotating shafts into the kinetic energy of a compressed medium. As is known by those of elementary skill in the art of engine design, engines may be used with a fuel to generate an area with a medium having a high pressure or a high velocity. The kinetic energy of a medium in the high pressure or high velocity area is then used in a motor to perform work, such as the mechanical rotation of a shaft.
Many engines can, essentially, be "reversed," such that when rotational force is applied to the shaft, the engine may operate as a compressor to convert the mechanical energy of the rotating shaft into the kinetic energy of a compressed medium. In fact, current turbine engines often have both compressor stages and motor driving stages.
Presently available turbines generally include axial rotors with extended blades. A medium under pressure or at high velocity, such as air, is applied to one end of the turbine rotor. The medium flows parallel the axis of the turbine rotor and perpendicular to the radius of the rotor to an area of lower pressure and higher velocity at the other end of the rotor.
The medium comes in contact with rotor blades placed at an angle relative to direction of both the axial travel of the medium and the rotation of the turbine. The rotational thrust is provided by the thrust of the medium on those rotor blades. In multi-stage turbines, stator blades may redirect the medium to flow parallel to the axis of the rotor.
Also well known to those skilled in the art is the water wheel turbine, where the medium flows parallel to the radius of the rotor, and perpendicular to the axis. These devices have blades which are parallel to the axis. The moving medium provides static thrust against those blades to make the rotor turn.
In many conventional turbines, it is often desirable to have low friction between the blades and the medium, as well as between the turbine and the medium. Friction may result in undesirable energy loss and turbulence. The force to move the rotor is not substantially dependent on friction between the medium and the rotor and blades. (The propulsion of the rotor is the "reaction" to the "action" of the medium pressing against the blades.)
Conventional axial turbine rotors and blades are often complex. Consequently, they are expensive and time-consuming to design, manufacture, maintain, and repair.
Moreover, a conventional axial turbine generally reaches its maximum rotational velocity as the speed of the medium, relative to the rotor and stator blades, reaches the speed of sound. If the medium velocity, relative to the rotor velocity, exceeds the speed of sound at any point in the turbine, the turbine can abruptly stop or, in some cases, be destroyed entirely.
The following U.S. patents are illustrative of the relevant art: U.S. Pat. Nos. 3,017,848, 3,150,816, and 4,422,822.